1. Field of the Invention
This invention relates to a process for preparing a laminate, in which an olefin polymer layer and a fluororesin layer are adhered to each other by fusion with the aid of an adhesive polymer.
2. Background Art
Fluororesins are excellent in resistances to chemicals, solvents and weather, and are free from stickiness. They are therefore utilized for various purposes.
However, since the nonstickiness of fluororesins brings about low adhesion between fluororesin layers and substrates of various materials, the fluororesin layers easily come off the substrates.
To improve the adhesive property of fluororesins, for instance, to enhance the adhesion between fluororesins and metallic substrates, the following methods have been devised:
a method disclosed in Japanese Laid-Open Patent Publication No. 1-149880, in which a composition comprising an epoxyacrylate resin, a vinylidene fluoride resin and a methacrylic resin is employed as a primer; and
a method disclosed in Japanese Laid-Open Patent Publication No. 1-146965, in which a composition comprising as essential components a polyol resin, a polyisocyanate compound and a thermoplastic acrylic resin is utilized as a primer.
However, a simple and satisfactory technique of adhering a layer of a fluororesin to a layer of an olefin resin such as polyethylene or polypropylene has not been known as yet.
SUMMARY OF THE INVENTION
The inventors of the present invention have succeeded in preparing a laminate of an olefin polymer layer and a fluororesin layer, in which these two layers are firmly adhered to each other by fusion with the aid of a newly developed primer effectively usable for fluororesins.
Thus, the present invention provides a process for preparing a laminate, comprising the step of adhering a layer of an olefin polymer and a layer of a fluororesin to each other by fusion with the aid of an adhesive polymer, the adhesive polymer being a polymerization product A prepared by copolymerizing a radical-polymerizable olefin polymer B, which is obtained by reacting an olefin polymer (a) having at least one functional group in one molecule thereof with a radical-polymerizable monomer (b) having a functional group which can react with the functional group contained in the olefin polymer (a), with a monomer (c) which comprises as essential components alkyl acrylate, alkyl methacrylate and/or a fluorine-containing unsaturated monomer and is copolymerizable with the radical-polymerizable olefin polymer B, the polymerization product A comprising from 10 to 90 wt. % of the monomer (c).
According to the present invention, an olefin polymer and a fluororesin can be firmly adhered to each other by using the specific polymer as an adhesive. Therefore, a laminate having both of the advantageous properties of fluororesins and those of olefin polymers can be obtained with ease and at low cost.